What is a behavior exhibited when all feathers of a bird are erected for comfort?

The behavior known as rousing occurs when a bird raises all of its feathers to help fluff them out for comfort and to maintain body temperature. This is often seen when a bird is resting, as it allows air to circulate through the feathers, providing insulation and helping to remove dust or debris. Rousing is a common behavior in many bird species and is essential for their well-being.

In contrast, the other options refer to different behaviors. "Gorge" typically pertains to a bird consuming more food than it needs in one sitting, often leading to overindulgence. "Hack" refers to the process of allowing a bird to fly and develop its skills in an open environment, which is part of training and acclimation. "Graze" relates to birds foraging for food on the ground, a behavior observed when they are feeding. Understanding these distinctions helps clarify why rousing is specifically associated with feather comfort and maintenance.